Wireless System Integration, Issues and Applications

Transcription

1 Wireless System Integration, Issues and Applications Emil Jovanov Electrical and Computer Engineering Dept. University of Alabama in Huntsville

2 Introduction Healthcare is the Largest Segment of US Economy $1.8 Trillion in 2004 (15% of GDP) $200 Million Informal Care Givers (1/3 of population) $4178 per capita (50% more than the next nearest nation) - US is less than 10th in life expectancy - US is 26th in infant mortality rates Pending Crisis Retiring Baby Boomers Elderly is the Largest Growing Age Group 45 million Uninsured ISSS MDBS 2006, Boston, MA 2

3 Motivation Current Healthcare Systems are Centralized, Focused on Reacting to Illness We are in need of Distributed Systems, Focused on Proactive Wellness Management Healthcare Spending by Category Drugs 15% Diagnostic 4% Causes of Death in the US in 2000 Tobacco 18.1% Poor diet and physical inactivity 16.0% Alcohol consumption 3.5% Microbial agents 3.1% Toxic agents 2.3% Motor vehicles 1.8% Firearms 1.2% Treatments, Hospital Stays, and Rehabilitation 81% ISSS MDBS 2006, Boston, MA 3

4 Motivation Goal: ubiquitous and affordable healthcare mhealth Mobile computing, Sensor technology, and Communication technologies WBAN emerging integration technology Promising technology for unsupervised, continuous, ambulatory health monitoring Challenge: design WBAN for extended RT of physiological data and events. Solution: hierarchical 3-tier ubiquitous monitoring system Opportunities: Ambulatory health monitoring Computer-assisted rehabilitation Augmented reality systems Long-term benefits: Promote healthy lifestyle Seamless integration of data into personal medical records and research databases Knowledge discovery through data mining Ultimate test? ISSS MDBS 2006, Boston, MA 4

5 Outline Introduction Proposed Solution: WBAN System Data Flow and System Requirements System Design Issues Conclusions Demonstration ISSS MDBS 2006, Boston, MA 5

6 Ambulatory Health Monitoring Wearable Systems For Health Monitoring Close monitoring of Vital Signs Quantitative Feedback Computer Assisted Rehabilitation Holter Monitors Data Recorders ( < 24 hours) Post-session Analysis Telemedicine Systems ISSS MDBS 2006, Boston, MA 6

7 CardioLabs Ambulatory Heart Monitoring Event-based Recorders Loop Recorders (32 min) Patient Presses event button during episode Data Extracted for Post-Analysis ISSS MDBS 2006, Boston, MA 7

8 CardioNet Mobile Cardiac Outpatient Telemetry Wireless Sensor and Wireless Monitor Arrhythmic event detection ISSS MDBS 2006, Boston, MA 8

9 Heart Rate Monitors Polar Electro, Suunto, Timex, Reebok, Integration into Fitness Equipment Real-time Heart rate Some Journal capabilities ISSS MDBS 2006, Boston, MA 9

10 ActiWatch Cambridge Neurotechnology Actigraphy Single Axis Accelerometer Clinical Research Sleep / Wake Patterns Sleep Disorders Periodic Leg Movement (PLMS) Infant Monitoring ISSS MDBS 2006, Boston, MA 10

11 Body Media (bodybugg) Multi-modal sensing Single axis-accelerometer (motion) (2) Temperature Sensors (heat flux) Galvanic Skin Response (GSR) Upload Data using USB Calorie Consumption Estimation Proprietary Algorithms ISSS MDBS 2006, Boston, MA 11

12 CodeBlue Harvard University, Boston University School of Management, and Boston Medical Center, 10Blade (start-up) Real-time Triage, Disaster Relief Pulse Oximeters, ECG, accelerometers ISSS MDBS 2006, Boston, MA 12

13 Wireless technologies WLAN and WPAN technologies Bluetooth Widespread, cell phones/pdas 720 kbps Relatively high power consumption, protocol stack complexity ZigBee Emerging standard Very low power 250 kbps UWB High bandwidth Alternative solutions MEMS resonators (100 µw) ISSS MDBS 2006, Boston, MA 13

14 Outline Introduction Proposed Solution: WBAN System Data Flow and System Requirements System Design Issues Conclusions Demonstration ISSS MDBS 2006, Boston, MA 14

15 WBAN Ubiquitous Health Monitoring ISSS MDBS 2006, Boston, MA 15

16 WBAN Configurations MS MS MS Internet Internet Internet HS WLAN WAN HS NC PS NC WBAN PS NC WBAN WBAN Sn S S S S Sn S S S S Sn S S S S ISSS MDBS 2006, Boston, MA 16

17 WBAN design goals minimization of weight and size of sensors, user s acceptance, portability, unobtrusiveness, ubiquitous connectivity, reliability, and seamless system integration. ISSS MDBS 2006, Boston, MA 17

18 Hierarchical organization Tier 1. Sensor 2. Personal server 3. Medical server Processing 1-10 MIPS ~ 100 MIPS ~ GIPS Power RAM 1-10 KB ~ 50 MB ~ GB Secondary KB, ~ 1 GB ~ TB memory 1 MB (flash) Power consumption 1-10mW proc. ~50mW comm. ~ 100 mw ~ 100 W Other Peripherals, timers, etc. WAN communication Internet connectivity ISSS MDBS 2006, Boston, MA 18

19 Wireless Body Area Networks at UAH 2000: Wireless Intelligent Sensors (WISE) 2002: Distributed Wireless System for Stress Monitoring 2004: ActiS Activity Sensor Standard sensor platforms and communication protocols A wireless body area network of intelligent motion sensors for computer assisted physical rehabilitation, Journal of NeuroEngineering and Rehabilitation, ISSS MDBS 2006, Boston, MA 19

20 ActiS: Activity Sensor ISSS MDBS 2006, Boston, MA 20

21 Telos Wireless Platform 8MHz Texas Instruments 16-bit MSP430F1611 microcontroller 10KB RAM, 48KB Flash Chipcon 2420, IEEE compliant wireless transceiver Hardware link layer encryption and authentication 250kbps, 2.4GHz programmable output power Onboard antenna Range: 50 m / 125 m Integrated humidity, temperature, and light sensors ADC, DAC, DMA,Supply Voltage Supervisor TinyOS support ISSS MDBS 2006, Boston, MA 21

22 Intelligent Signal Processing Modules First generation MSP430F1232 microcontroller 256B RAM, 8KB ROM 2 Dual Axis ADXL202 Acc. Bioamplifier (ECG, EMG) Force resistor signal conditioning circuit (foot switch) Second generation MSP430F1611 microcontroller 10KB RAM, 48KB ROM Single 3D Acc (Freescale) Bioamplifier (ECG, EMG) ISSS MDBS 2006, Boston, MA 22

23 ZigBee network controller Wireless gateway ARM7 processor ~60MIPS proc. power 64KB RAM Compact Flash interface ZigBee wireless interface ISSS MDBS 2006, Boston, MA 23

24 Actis System Performance Tier 1. Signal Processing 2. Sensor Platform 3. Wireless Gateway 4. Personal Server Module Processing 1 MIPS 1 MIPS 60 MIPS ~ 100 MIPS Power RAM 256B 10 KB 64 KB ~ 64MB Power consumption 1 mw 3mW 60 mw ~ 300 mw ISSS MDBS 2006, Boston, MA 24

25 Outline Introduction Proposed Solution: WBAN System Data Flow and System Requirements System Design Issues Conclusions Demonstration ISSS MDBS 2006, Boston, MA 25

26 WBAN System Design WBAN is a collection of sensors Each sensor monitors one or more signals Signals can be used for raw data acquisition or on-sensor signal processing Raw sample set Processed events generated from raw data e.g. step event or heart beat event Example: 3 channel ECG with upper body tilt may generate the following streams: 3 ECG signal streams 1 heart beat and 1 ischemia event stream 3 accelerometer streams 1 tilt stream ISSS MDBS 2006, Boston, MA 26

27 WBAN System Design Required system bandwidth (SBW): where: SBW N Nch = i i= 1 j = 1 Fs i SS N is the total number of sensors in the system (WBAN) Nch i is the number of channels of the signal i Fs i is sampling frequency of the signal i SS i is sampling frequency of the signal i Rov i is the record message overhead of the signal i: Message _ overhead + primary _ data _ size Rov i = i Rov i i primary _ data _ size i i ISSS MDBS 2006, Boston, MA 27

28 System Design typical requirements ECG Nch i Fs i SS i BW i = [1..3] [ ] [12..16] = [3, ,000] bps EEG Nch i Fs i SS i BW i = [1..8] [ ] [12..16] = [1, ,000] bps ISSS MDBS 2006, Boston, MA 28

29 System design on sensor processing On-sensor processing reduces required communication bandwidth - SBW Example: Heart beat events (Rpeak event) Rpeak Nch i Fs i SS i BW i = [1] [0.6..4] [16] = [ ] bps ECG: [3, ,000] bps Local Intelligence always pays off ISSS MDBS 2006, Boston, MA 29

30 3-tier Hierarchical Organization ISSS MDBS 2006, Boston, MA 30

31 Wireless Integration MS Database Internet Internet Gateway WLAN/ WAN PS NC Record collections Records WBAN Events Sn S S S Raw data ISSS MDBS 2006, Boston, MA 31

32 Data Flow Sensor #1 Intelligent Sensors Sensor # M WPAN WPAN Home Server + WPAN Gateway Medical Server Internet Storage ISSS MDBS 2006, Boston, MA 32

33 Data flow memory requirements On-sensor secondary storage Flash memory M 2 On-sensor flash drive M 3 Sensor #i RAM M 1 CPU ISSS MDBS 2006, Boston, MA 33

34 System Design raw data buffering On-sensor memory storage M 1 RAM memory capacity (5KB) M 2 flash memory capacity (4Mb) M 3 flash disk capacity (1GB) System operation time (ECG sensor) OT = M i / BW i OT 1 (RAM) = M 1 / BW ECG = 5 KB * 8 b/b/ [3, ,000] bps [2..14] s OT 2 (flash) = M 2 / BW ECG = 4Mb / [3, ,000] bps [ ] hours OT 2 (flash_disk) = M 3 / BW ECG = 8Gb / [3, ,000] bps [4..31] days ISSS MDBS 2006, Boston, MA 34

35 System Design event buffering On-sensor memory storage M 1 RAM memory capacity (5KB) M 2 flash memory capacity (4Mb) M 3 flash disk capacity (1GB) System operation time (Rpeak events) OT 1 (RAM) = M 1 / BW Rpeak = 5 KB * 8 b/b/ [ ] bps [11..71] min OT 2 (flash) = M 2 / BW Rpeak = 4Mb / [ ] bps [6..41] days OT 2 (flash_disk) = M 3 / BW Rpeak = 8Gb / [ ] bps [4..28] years ISSS MDBS 2006, Boston, MA 35

36 UAH on-sensor buffering Each sensor uses RAM buffering as a primary storage Flash buffering as a secondary storage Reliable operation Out of range situations ISSS MDBS 2006, Boston, MA 36

37 Record Update Mechanism Raw Data / Events File 3 File 2 File 1 Connection Made Data is written to permanent storage Update Queue Destination ISSS MDBS 2006, Boston, MA 37

38 Packet uploads Out of range Upload bursts ISSS MDBS 2006, Boston, MA 38

39 Event Management x accx 104 accy Motion accz Sensor 1 (TS2) ECG 3000 Sensor (TS1) Heart Beat Heart Beat Step Heart Beat Step Beacon Message Event Message with Timestamp Beacon Message NC TS1 TS2 TS3 NC TS1 TS2 TS3 Frame i-1 Frame i ISSS MDBS 2006, Boston, MA 39

40 Outline Introduction Proposed Solution: WBAN System Data Flow and System Requirements System Design Issues Conclusions Demonstration ISSS MDBS 2006, Boston, MA 40

41 System Design Issues Extremely low-power, low-weight, and small size Non-invasive and unobtrusive operation Reliable transmission using retransmissions Time-stamping for collective processing and out of order message processing Interoperability requires standardization Seamless connectivity Application specific standards for wireless communications, messaging, and system support Seamless customization, configuration, and integration Sensor placement and mounting Sensor commodization Security and Privacy Communication and data storage User compliance, efective user interfaces ISSS MDBS 2006, Boston, MA 41

42 Time Synchronization Necessary for collective processing, data logging, power-efficient operation, etc. Problem: High precision synchronization with low frequency clocks 32 KHz on Telos FTSP FloodingTime synchronization protocols Telos specific implementation at UAH Implemented precision ~2 µs with 32KHz crystal! ISSS MDBS 2006, Boston, MA 42

43 Mechanism for Time Synchronization Data transmitted over RF SFD Capture Timer Process Send Preamble SFD Length MAC Protocol Data Timestamp Propagation Data received over RF Preamble SFD Length MAC Protocol Data Timestamp SFD Capture Timer Synchronize local time (TinyOS) Network Coordinator ISSS MDBS 2006, Boston, MA 43

44 Power Consumption User s convenience Battery life Size and weight of batteries Battery Life Battery Capacity [mah] BL = BC / I ave For simple time keeping and minimal processing average power is ~2.1µA, standard 750 mah batteries will allow battery life: BL = 750 mah / 2.1 µa 44 years!!! Introducing: Apple Computers ISSS MDBS 2006, Boston, MA 44

45 Power efficient communication Wireless communication requires ~ 10 times more power than processing Turn-off radio whenever you can Time slots Time slot scheduling Allow time slots for new sensors to join the club Design issues: Battery life Latency Number of sensors ISSS MDBS 2006, Boston, MA 45

46 Power efficient wireless communication - implementation Power supply current on sensor 20 Listen Transmit 15 I [ma] 10 5 Idle Time [sec] I [ma] Super cycle time in this example is 1 sec. Sensors listens at the beginning of each cycle for 50ms, and transmits its own messages (2 in this example) in predefined time slot Time [sec] ISSS MDBS 2006, Boston, MA 46

47 Personal Server program Implemented on PC/PDA Controls the network of wireless sensors Collects data from sensors Communicates with servers on higher levels of hierarchy whenever the connection is available Provides feedback and alerts to the user Stores user s inputs ISSS MDBS 2006, Boston, MA 47

48 ActiS Monitor User s Info ISSS MDBS 2006, Boston, MA 48

49 ActiS Monitor Signals and Graphs ISSS MDBS 2006, Boston, MA 49

50 Privacy and Security Hardware encryption of wireless communications Standard security mechanisms from the personal server to the upper levels of hierarchy ISSS MDBS 2006, Boston, MA 50

51 Outline Introduction Proposed Solution: WBAN System Data Flow and System Requirements System Design Issues Conclusions Demonstration ISSS MDBS 2006, Boston, MA 51

52 Conclusions Promising technology for Ambulatory monitoring Early detection of abnormal conditions Supervised rehabilitation Advantages Promotes healthy lifestyle / health awareness Increased confidence and better quality of life Data mining of huge research databases Effects of drug therapies and rehabilitation procedures Need for standards for wireless communications, messaging, and system support ISSS MDBS 2006, Boston, MA 52

53 Acknowledgments Aleksandar Milenkovic, Chris Otto, Corey Sanders, John Gober, Reggie McMurtrey, University of Alabama in Huntsville Piet de Groen, Bruce Johnson, Mayo Clinic Steve Warren, Kansas State University ISSS MDBS 2006, Boston, MA 53

54 Outline Introduction Proposed Solution: WBAN System Data Flow and System Requirements System Design Issues Conclusions Demonstration ISSS MDBS 2006, Boston, MA 54